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Evolutionary roots of freedom
To give up the illusion that sees in it an immaterial "sub
stance" is not to deny the existence of the soul, but on the
contrary to begin to recognize the complexity, the richness,
the unfathomable profundity of the genetic and cultural her
itage and of the personal experience, conscious or otherwise,
which together constitute this being of ours: the unique and
irrefutable witness to itself.
Jacques Monod
It is virtually impossible to discuss the cerebral foundation of
liberty without dealing with the evolution of the brain. The reason
is simple: The capacity of mammalian organisms to modify their
environment by choice and to adapt to it by chosen means has
grown enormously with the evolutionary growth of certain parts
of their brain, the cerebral cortex in particular. Most relevant to
our present discourse is the cortex of the frontal lobes. It is indeed a
remarkable fact with a touch of cosmic irony that the science of
evolutionary neurobiology, which can only "postdict" but not pre
dict, has unveiled in the prefrontal cortex of man the seed of his
future, the capacity to predict and to turn prediction into action
that will impact on that future and on that of human society.
The prefrontal cortex is the vanguard of evolution in the
nervous system. Yet it is one of the latest cerebral structures to
develop, in evolution as in the individual brain (Preuss et al., 2004;
Rilling, 2006; Schoenemann et al, 2005; Sowell et al, 2003).
Language and prediction, the two most distinctively human
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Evolutionary roots of freedom
functions that the prefrontal cortex supports, are anchored in the
history of the species, as is the structure of the prefrontal cortex
itself. In the human brain, the latter is tied to its evolutionary past
and to the future it anticipates. Thus, while the human brain
cannot predict evolution, it can predict the consequences of its
actions, with them to predict and shape further actions in a
continuous cycle, the perception/action (PA) cycle, which func
tionally links the organism to its environment. The prefrontal
cortex is the highest structure in that cycle, which integrates the
past with the future - however near or distant either is - in the
course of behavior, language, and reasoning.
The PA cycle also has deep roots in evolution. In lower
animals, earlier precursors of it mediate the adjustment of the
organism to the surrounding world (Uexkull, 1926). The human
brain, which sustains the PA cycle with the cortex, is the most
complex adaptive system in the universe. It is an open system like
all living systems (von Bertalanffy, 1950). As such, it is perma
nently in quasi-equilibrium, but also in constant exchange with
its environment to maintain that equilibrium. Thanks to its pre
frontal cortex inserted in the PA cycle, the human brain, unlike
any other, develops a prospective temporal dimension. Thereby,
it makes advanced long-term adaptive changes in its environ
ment. Furthermore, language endows the human brain with the
ability to record those changes, to codify them, and to institution
alize them.
In short, the prefrontal cortex confers on the human brain
the capability to predict and, accordingly, to preadapt. Lower brains
have a measure of that capability, as well as certain primitive
forms of communication with conspecifics that may be the ata
vistic precursors of language. But the transition from the simian
to the human in power of prediction and preadaptation, as well as
communication, is so dramatic as to constitute a veritable quan
tum leap. All relevant variables (complexity, time, "vocabulary,"
and so on) increase by several orders of magnitude. Along with it,
variability increases immensely, so do the options for choice
among alternatives. In fact, those comparative increases over
other species are so large that the argument about functional
homologies between humans and animals, even the great apes,
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Evolutionary roots of freedom
becomes well-nigh irrelevant. So does the discussion as to
whether in evolution we are dealing with qualitative or merely
quantitative differences in continua (Bolhuis and Wynne, 2009).
With the advent of the human prefrontal cortex all the animal
precursors ofcognition - intelligence and communication among
them - open widely to a future agenda.
This does not mean that the structure and workings of the
animal brain are irrelevant to our understanding of the neuro
biology of freedom. Quite the contrary; it is only in the brain of
the animal, especially the nonhuman primate, that we can practi
cally study the basic organization of knowledge, feelings, and
values that give the human his or her freedom to make choices.1
In the animal brain we can investigate the mechanisms of the PA
cycle behind choice, planning, decision-making, and the tempo
ral organization of behavior. All of them are functions in which,
as we will see, the prefrontal cortex plays a critical role. Those
mechanisms constitute the underpinnings of human liberty, cre
ativity, and their myriad expressions.
Freedom, the capacity to choose between alternatives,
emerges from the activity of cortical-cell networks of perceptual
and executive memory, at the confluence of multiple converging
inputs from past memory with multiple diverging outputs to
future action. Freedom is a phenomenon of the brain's selection
between those inputs and between those outputs for adaptive
purposes. As a result of evolution and development, the cerebral
cortex and freedom adopt in the human pivotal positions
between an experiential convergent past and a divergent future
of possibilities - and probabilities.
1 To be sure, no animal is amenable to the study of the semantic aspects of
language and, least of all, to the neural mechanisms at their foundation. But
many animal species lend themselves well to the exploration of the neural
mechanisms of the temporal organization of information that language
shares with all other cognitive functions. Those mechanisms are not directly
accessible in the human brain, even with modern imaging methods. Needless
to say. only in the absence of stress or pain are cognitive functions testable in
animals; this imposes strict scientific - in addition to ethical - constraints on
animal experimentation.
Evolution of the cerebral cortex
EVOLUTION OF THE CEREBRAL CORTEX
Two approximate dates within wide uncertain ranges are
especially relevant in the history of brain evolution: one 250
million years ago, and the other 250 thousand years ago. The
first, in early Mesozoic, marks the appearance of the first mam
mals, the second the appearance ofthe last hominid, Homo sapiens.
The brains of fishes, amphibians, and reptiles were - and are covered by an evolutionally ancient cortex-like structure named
the pallium (mantle). The pallium is divided into two compo
nents, the hippocampal cortex situated next to the brain's mid
line, and the piriform cortex, lateral to the hippocampal
cortex (Figure 2.1). A third "pallium" will emerge between the
two that in Homo sapiens will constitute 80 percent of the
entire mass of the brain: the neocortex.
B
Dorsal
cortex"
Hippocampal
cortex
Piriform
cortex
Amphibians
Reptiles
Mammals
Opossum
Human
Figure 2.1 Evolutionary development of the cerebral cortex.
A: Lengthwise sections of the brains of four classes of vertebrates.
P, pallium, generic name for cortex, both old and new
(phylogenetically). From Creutzfeldt (1993). B: Crosswise sections
of the brains of a primitive amphibian (Neclw-us), the box tortoise
(Cistudo), the opossum (Didelphis), and the human being. From
Herrick (1956), modified.
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The neocortex or neopallium, the "new" cerebral cortex of
the mammalian brain, remains physically wedged between the
two ancient cortices, the hippocampus and the piriform cortex.
The developing neocortex crowds the hippocampus toward
the midline and the piriform lobe (piriform cortex and amygdala)
toward the lateral underside of the brain. In later mammals,
the neocortex grows heffily, pushing the two ancient cortices
toward each other in the middle of the cerebral hemisphere.
These two ancient cortices, even in the mammalian brain,
preserve some of the functions they perform in primitive species:
the sensing of life-sustaining signals, such as taste, olfaction, and
spatial orientation. Additionally in primates, the hippocampus is
involved in the acquisition and retrieval of memory, while the
amygdala is involved in emotion, endowing memories with
feeling.
In the course of evolution, the neocortex, among all brain
structures, increases the most in size, especially in primates. That
evolutionary growth of the neocortex is exponential, out of pro
portion with the growth of other structures. Further, the volu
metric expansion ofthe neocortex occurs concomitantly with the
differentiation of its cellular architecture, culminating in the
human brain with a relatively large size and marked lamination
of its cellular structure (six layers of neurons of different sizes,
shapes, and densities). These changes, embedded in the human
genome, appear to be the result of selective upregulation of gene
expression2 relative to nonhuman primates (Preuss et al, 2004).
Through those changes, and concomitant genetic mutations,
humans have evolved mechanisms that allow them to overcome
the physical constraints that impede the course of their own
evolution (Krubitzer, 2009). Among the changes are those that
take place in cortical architecture. Clearly, the evolutionary
growth and differentiation of the neocortex has much to do
with the increased ability to adapt to the environment and with
2 Upregulation refers to the increase in the capability of a gene to express cell
products (e.g., specific proteins) in response to internal or external stimula
tion, as, for example, an immune antibody to a new virus or an antitoxin to a
new chemical agent.
Evolution of the cerebral cortex
the prolongation of life. In the human brain, that cortex has
developed a large number of specialized areas to respond to all
manner of sensory signals as well as to execute all manner of
skillful movements.
In brain evolution, the greatest neocortical expansion takes
place in areas called "of association," which serve the higher
cognitive functions; that is, those functions that deal with knowl
edge and memory. Naturally, they deal as well with the neural
transactions between the organism and the environment that
depend on those functions. In the human brain, there are two
separate cortical regions with areas of association. One is in the
posterior part of the brain, extending over large portions of the
parietal, temporal, and occipital lobes (PTO region), which con
tains networks of knowledge and memory (cognits) acquired
through the sensoiy systems. Those networks or cognits serve
the highest aspects of cognition, including perception, language,
and intelligence. The other associative region is the prefrontal
cortex, the association cortex of the frontal lobe, which serves the
executive aspects of cognition, especially the temporal organiza
tion of actions in the domains of behavior, language, and reason
ing. This "executive" cortex develops maximally in the human
brain,3 where it occupies nearly one-third of the totality of the
neocortex (Figure 2.2).
Especially relevant to the development of the distinctive
cognitive prerogatives of the human in language, planning, and
Primarily on the basis of morphological imaging data (Semendeferi et ah,
1997), it has been argued that the prefrontal cortex does not evolve more, in
proportion, than other cortical areas. Whereas this may be true volumetrically
for the entirety of the frontal cortex, it does not take into account the fine
structure of cells and fiber connections that characterize the prefrontal cortex
perse. In the primate, anyhow, the frontal region that association nuclei of the
thalamus innervate, which we call the prefrontal cortex, considerably exceeds
in size the region they innervate in the posterior - perceptual - cortex (Jones
and Leavitt, 1974; Walker, 1940). Further, on cytoarchitectonic grounds, the
prefrontal cortex, which roughly corresponds to what Brodmann (1909,1912)
called the regio frontalis (that is, all frontal areas minus areas 4 and 6),
constitutes, by his calculations, 8.5% in the lemur, 11.5% in the gibbon and
the macaque, 17% in the chimpanzee, and 29% in the human, of total cortex.
On that basis alone, it seems legitimate to speak, figuratively, of an evolu
tionary "prefrontal explosion" in the human.
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Evolutionary roots of freedom
Figure 2.2 Relative size of the prefrontal cortex with respect
to total cortex in six animal species (marked by shading
of external and internal hemispheric surface). PTO,
parieto-temporo-occipital association region (posteriorassociation
cortex).
the exercise of freedom is the evolution of connections between
prefrontal neurons and those of other cortical areas. Those
connections, together with the neurons they link, constitute the
essential components of the neural infrastructure of cognitive
networks, and thus of all the cognitive functions of the cerebral
cortex.
Individual development of cerebral cortex
The most rapid and efficient connectivity in the brain is that
consisting of fibers surrounded by myelin,4 which constitute the
bulk of the subcortical white matter and of the corpus callosum, the
large commissure that connects the cortices ofthe two hemispheres
together. It is the white matter, more than the gray - cellular matter of the cortex that increases the most in evolution. That is a
clear indication of the vast expansion of the connective potential to
form neural networks, which the human cortex requires in order to
deal with the complexities of the world around it.
Among all the connective tracts with which the human
brain is endowed, probably none is more important for cognition
than the one that links, in each hemisphere, the posterior (PTO),
perceptual, cortex with the prefrontal, executive, cortex: the
superior longitudinal fasciculus. The connections within that
tract are bidirectional; in other words, they run in both direc
tions, some PTO to front and others front to PTO. They constitute
the backbone of the PA cycle, connecting posterior and frontal
cortices reciprocally in tandem function. They will become essen
tial for all kinds of temporally structured behaviors, where per
ception will guide action, and vice versa, through the
environment. Most importantly, they will be essential for the
spoken language in dialogue, where the environment includes
the interlocutor (Chapter 6).
INDIVIDUAL DEVELOPMENT OF THE CEREBRAL
CORTEX
An old idea, first promulgated in 1899 by Ernst Haeckel
(1992), is that ontogeny, the early development of an individual,
recapitulates phylogeny, the development of the species. Indeed,
many features of the individual nervous system of the human
appear to develop in the same sequence they followed in the
course ofevolution as a result of natural selection - that is, during
the development of earlier animal species. Such features include,
4 Myelin is a white substance made of proteins and lipids that forms a sheath
around the rapid-conduction fibers (axons) of the brain. It is indispensable for
proper cortical integration and coordination.
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Evolutionary roots of freedom
for example, the prefrontal cortex, which develops late in
evolution and does not develop fully until the third or fourth
decade in the life of the individual.
Haeckel's recapitulation idea is basically flawed in one
important respect. Whereas natural selection follows a passive
process based on random genetic variance and mutation,
ontogeny follows an order established by biological clocks that
determine gene expression and molecular-enzymatic change jointly with environmental influences from point of conception
onward. Nevertheless, Gould (1992) attempts to reconcile the
two trends, phylogenetic and ontogenetic, by proposing the
concept of "heterochrony." Heterochrony would simply
signify the change, in the development of the individual
organism, of the relative rate and timing of appearance of char
acters already present in ancestors. In other words, ontogeny by
its own clock would compress, extend, and retime the results of
evolution.
The concept of heterochrony would legitimize the predic
tion of ontogeny based in part on the postdictable evolution of
traits, but that would still leave that prediction subject to the
uncertainties surrounding lineage and ancestry in evolution. In
any event, it would be wrong to deny or obscure the evidence that
the development of the human brain to adulthood entails the
development of social traits already present in the behavior of
most animal populations. Among those traits are the inborn
tendencies to affiliation, trust, group protection, and hierarchical
social structure. Consequently, it is fascinating to study brain
development in the attempt to glean how it relates not only to
the development of cognitive functions that are distinctly
human, such as prediction and language, but also to the develop
ment ofsocial dynamics already present in ancestral populations.
Both issues bear on the roots of freedom.
There is an added incentive to study the ontogeny of the
brain from an evolutionary point of view. It is now increasingly
evident that, just as in the evolution of species and traits, in
ontogeny the development of the brain's features and functions
is the result of dynamic interactions between the elements of
biological populations: gene populations, neuron populations,
Individual development of cerebral cortex
synaptic populations, network populations, and nerve fiber
populations.
The neonate comes into the world with the structure of the
cerebral cortex practically complete, with all its principal ele
ments in place. The neocortex, the "new" cortex in evolutionary
terms, is already characterized by its laminar structure, the pres
ence in it of the major types of nerve cells, synapses, and other
contacts between cells, as well as the major excitatory and inhib
itory chemical neurotransmitters.5 In quantitative terms, how
ever, certain fluctuations occur over time in the relative
amounts of those elements. There are periods of exuberant pro
duction of neurons followed by periods of attrition in their num
bers. The same may be said for synapses and other elements of
cellular architecture. From the beginning, however, there is a
gradual and more or less continuous increase offiber connections
between cells in most all layers of the neocortex (Figure 2.3). This
increase in connectivity persists into adulthood and is most mani
fest jn the myelination - covering with myelin - of long fiber
connections between cortical areas. This translates itself into
general increments of cortical white matter even in the presence
of some relative decrements in gray matter.
The age-related increase in cortical connectivity is critical
for cognitive development, and, therefore, for the development
of free will. Connectivity is essential to a relational code, such as
the code of cognition and of the cognits of memory and knowl
edge.6 Cognits are defined by relationships between elements
(neurons or assemblies of neurons) that represent discrete com
ponents of a memory or item of knowledge (Chapter 3). Byvirtue
of the combinatorial power of connections, an also discrete num
ber of neuronal assemblies can encode, by combination and per
mutation, an almost infinite number of different items of
The most important excitatory neurotransmitters are glutamate, norepi
nephrine, serotonin, dopamine, and acetylcholine (Siegel,1999).The concen
tration of each of these varies somewhat from area to area. By far the most
important inhibitory transmitter is the ubiquitous gamma-aminobutyric acid
(GABA).
A study of brain connectivity by reliable neuroimaging reveals the age-related
enhancement of cortico-cortical connectivity in children performing cogni
tive tasks, such as listening to stories (Karunanayaka et al., 2007).
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Evolutionary roots of freedom
3 mo.
6 mo.
15 mo.
24 mo.
Figure 2.3 Development of neurons in the human cortex. Top:
Prenatal period, from 10.5 weeks to birth. From Mrzljak et al.
(1990), with permission. Bottom: Postnatal, at 3, 6,15, and 24
months. From Conel (1963), with permission.
memory or knowledge. The same can be said for the cognits and
the relationships between them, which can be part of larger
cognits. In fact, it is that combinatorial power of connections
that gives us the individuality of our memory and of our actions.
The existence of more synaptic connections than neurons
can provide the executive cortex, especially the late developing
cortex, with enormously diverse inputs and outputs. Thus the
prefrontal cortex can thereby give rise to - i.e., organize - an
immense number of alternative actions. Given that cortical con
nectivity increases with age at a higher rate than brain mass, it is
reasonable to conclude that the options ("choices") of both inputs
Individual development of cerebral cortex
to and outputs from the executive cortex also increase with age at
a very high rate. The same is true for freedom, which is in essence
the capacity of that cortex to selectively favor or bias inputs and
outputs.
The best direct evidence of the age-related increase and
reinforcement of cortical connectivity is the age-dependent mye
lination of long cortical nerve fibers. We have known for over a
century, since the seminal work of Flechsig (1901), that around
the time of birth cortical myelination follows a certain chrono
logical order, which can be discerned by histological fiberstaining methods (Figure 2.4). The first to myelinate are the
sensory and motor areas of the cortex. From then on, myelination
takes place in progressively higher areas ofassociation.7 The last
areas to fully myelinate are those of the posterior and frontal
association cortices (white in Figure 2.4). Thanks to modern scan
ning methods, we now know that the prefrontal cortex does not
reach full myelination until the third or fourth decade of life
(Sowell et al, 2003). The implications of this fact are profound,
especially as they relate to cognitive maturity and, of course,
freedom of action and responsibility for it.
Assuming that the degree of myelination is related to neural
maturation generally, and assuming further that neural matura
tion is related to psychological maturation, it is reasonable to
speculate on the age-related neural constraints of psychosocial
development. For example, it seems more than just possible that
much of the turmoil of adolescence is caused by an imbalance
between the two sides, emotional and cognitive, of the PA cycle.
On the one side is the input from emotional centers under the
onslaught of massive hormonal changes; add to that the exigen
cies ofgratification in the presence of still immature principles of
behavior. On the other side is an immature prefrontal cortex
7 The staining of myelin in anatomical specimens of the cerebral cortex is not a
simple matter. It is a laborious technique subject to errors, some of which have
been pointed out by seasoned neuroanatomists as possibly having distorted
Flechsig's original observations. Nonetheless, whereas some quibble about
the precise order of myelin formation as portrayed in Figure. 2.4, there is
general consensus on the conclusion that the process commences in primary
sensory and motor areas and continues through the association cortex.
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Evolutionary roots of freedom
Figure 2.4 Numerical order of myelination of areas of the human
cortex, according to Flechsig. Primary sensoiy and motor areas
(low numbers, in black) myelinate first; association areas (high
numbers Inwhite) myelinate last. From Bonin (1950), modified.
ready for physical action without the capacity, yet unavailable,
for reasoning or good judgment. The result is self-oriented and
self-adjudicated liberty with minimal responsibility, characteris
tics of the typical teenager.
Neural Darwinism
By age 20, freedom has in most individuals acquired a social
dimension, and with it the social responsibility that constrains,
or rather complements individual freedom, is nearing its adult
plateau. The third decade oflife calls for sharp cognitive decisions
on one's future. By then, full maturity is reaching the highest
areas of cortical association. With it the brain reaches the peak of
inventive capacity and imagination. With the maturation of the
prefrontal cortex in particular, language and the capacity to pre
dict expand, and with them the capacity for social planning with
common purpose. Those capacities will lead to decisions at
higher level, together with more freedom to lead others to greater
enterprises - educational, scientific, artistic, legislative, sporting,
and so on. It is the time when careers get started, superior studies
undertaken, and plans made for emotional, professional, or social
associations with others.8 With further cortical maturation, more
elaborate, complex, and abstract cognits are acquired and con
solidated in the cortex as part of the individual's experience.
These cognits include, among others, principles of altruism and
social justice.
NEURAL DARWINISM
The brain is essentially the organ by which the animal,
through sensing and acting, adapts to its environment. As such,
the brain develops modes to adapt to that environment that are
similar, if not identical, to those that guided evolution. A princi
ple of development that applies to ontogeny as well as evolution
is natural selection. To be sure, natural selection works for grow
ing individuals in different ways than for growing species. But its
s Nonetheless, it is somewhat simplistic to ascribe the acquisition of any given
social trait to narrower chronological age spans. In the first place, any plfenotypical trait at any age is the result of the interaction of genetic factors with
environmental factors. There is individual variance in both sets of factors.
Environmental factors intervene at different ages depending on internal con
ditions, such as hormonal levels. That interaction, in turn, leads to changes in
social interaction. To this we have to add the imponderables of individual
differences in nervous and hormonal maturation. The result is a long and
complex series of PA cycles between the individual and society that defy
precise chronological bracketing.
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Evolutionary roots of freedom
adaptive results are similar, and to some extent parallel and
synergistic.
Something radically new, however, takes place in the
human brain that is unprecedented in prior evolution. Largely
on account of the extraordinary evolutionary growth of its pre
frontal cortex, the human brain "opens" to the future. Selection
is no longer between items of information or action that have
occurred in the past or are to occur in the immediate future. The
cerebral cortex of the human has become predictive. With that
change, selection can be made between anticipated options of
percept and action to occur in the future. Caution is needed
here, however. The anticipating agent is not consciousness, the
"ego," or some other subjective entity. It is the cortex itself, which
by predicting becomes preadaptive. Our will is as free as our
cortex is free to select future actions and prepare for them.
It is as if human development had forced a Copernican shift
on evolution, from the past to the future - a shift, nonetheless,
that does not change the basic principles of selection, variance,
and probability that move evolution under the umbrella of adap
tation. There are, however, two new principles that appear with
the human's prospective adaptation: teleonomy and affordance,
which I shall discuss later.
Under the title Neural Darwinism (1987), Edelman proposed a
new theory that applies evolutionary principles to the individual
brain. His theory of neuronal group selection (TNGS) relates to the
formation or modulation of brain circuits as a result of the sensoiy
contacts of the organism with its environment. Originally, the cor
tex and its link to the outside - that is, the thalamus - come into this
world with a genetic endowment of what he calls a primary reper
toire of interconnected neuronal groups in the two structures.
Through interactions of the animal with the environment, and the
neurobiological mechanism by which "cells that fire together wire
together," a secondaiy repertoire of cell groups will be formed. This
secondary repertoire will emerge at the expense ofthose cell groups
not selected, which will wither away - in correlation with the
observed postnatal attrition of cells and synaptic contacts. The
selected groups will self-reinforce their connections by circuit re
entry - output returning as input. In this manner perceptual
Neural Darwinism
experience will be acquired and registered in thalamic-cortical cir
cuitry. A similar argument can be applied to the dispersed neuronal
groups of the cerebral cortex, which, if they fire together, will wire
together into cognitive networks. Re-entry is the universal consolidator and activator of those networks.9
Regardless of the precise role of genetics in phylogeny and
ontogeny, the fact remains that in the nervous system certain
principles apply to both. These principles generally apply to the
adaptation of all biological organisms to their environment and
are unmistakably present in both phylogeny and ontogeny. They
include variance, selection, and probability. In the human organ
ism, with its prospective properties, we have to add teleonomy
and affordance (below).
Variance is the essential precondition of evolution. It is in
response to variance, whether in random gene mutation or in
environmental change, that natural selection occurs. Traits, fea
tures, competitive advantages, and so on are selected by nature
(note the passive voice) to adapt the organism to its environ
ment; the adaptation occurs at the level of the population of the
species - indeed, evolution is a population phenomenon - with
the end result of furthering survival and procreation. Much of the
selective adaptation, of course, takes place in the nervous system.
Variance in the nervous system, at the interface of the organ
ism with the environment, also serves selection and adaptation in
the individual. Here, however, the selection - say, between sensory
inputs and between actions - is active - that is, from the organism
outwards. As in evolution, the selection is adaptive, but now the
organism exercises it actively on the world. Evolution has in fact
given the individual the means to do it by itself. As in evolution,
selection serves the adaptive ends of the population, beginning
with brain cells and circuits and extending to the social order.
9 The Darwinian aspects of the TNGS can be criticized by the same argument
that distinguished the role of evolution from that of ontogeny in the forma
tion of neural structure. Even Gould's concept of heterochrony does not quite
reconcile the two. Thus, in the defense of neural Darwinism, the latter has
been simply referred to by some as a metaphor of the evolutionary process.
Nobody disputes, however, the critical importance of re-entry in the structural
and functional development of the cerebral cortex (Edelman, 1987).
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Evolutionary roots of freedom
Selection takes place in all the interactions ofthe brain with
the milieu, both internal and external. It serves the related
purposes of economizing resources and increasing efficiency.
On both counts, selection works on all percepts and all actions.
In those two domains, selection performs two separate but syner
gisticadaptive functions: (1) categorizingand (2) discriminating.
Perception is the categorizing of the world that surrounds
us (Hamad, 2005; Hayek, 1952). We perceive, that is, categorize
objects by virtue of their common features and the relations
between their parts (next chapter). The identity of an object
stays the same despite wide variations in size or other features
of its parts, provided that the relations between some of those
parts stay the same ("arose is a rose is a rose," despite differences
in color, shape, size, or fragrance). This is the fundamental psy
chological principle of perceptual constancy, which says that we
perceive an object as the same regardless of variations in size,
perspective, color, shape, and so on.
In our daily life we continuously perceive - mostly uncon
sciously - the objects and events around us by classifying those
objects and events into categories, and by matching them to
previous experience - that is, by matching them to established
cognits in our cortex. Conversely, we distinguish and discriminate
between objects and events as we concentrate on their individual
features (a yellow rose is different from a red rose). Categorizing
and discriminating are tandem functions in the establishment of
sensoiyorder in our cortex(Hayek, 1952). Theyguide not only our
ordinary life but also our scientific endeavors. Deduction and
induction, generalization and analysis, depend on them.
The two selective functions of categorizing and discriminat
ing also operate on the side of action. Now the categorizing
principle is the purpose or goal of the action. Many possible
movements can lead to the same outcome. We may call this
function "action constancy." At the same time, large goal-directed
movement is composed of small subcomponents to attain differ
ent subgoals on the way to a major goal (Bernstein, 1967).
Clearly, the categorizing of either perception or action in
the nervous system cannot be accomplished without something
akin to the principle of degeneracy of Edelman (Edelman and
Neural Darwinism
Gaily, 2001). In essence, degeneracy refers to the fact that in the
brain, as in other complex systems, multiple inputs can lead to
the same output.10 No organism could survive without it.
Degeneracy, or something like it, is at the root of perceptual
and motor constancy.
The cerebral cortex is permanently in a state of internal
change, yet that change tends to equilibrium at some point in the
future. The billions of neurons concomitantly active in the vigilant
cortex, whose electrical activity is characterized by "desynchron-
ized" rhythms,11 would bombard sensoiy and motor centers with
such a diverse flow of impulses that those centers would easily be
led to chaos. In the absence of degeneracy, in other words, in the
absence of the capacity to generalize across inputs or outputs, no
stable perception or action would be possible.
In the state of attention, a cognitive function that is selective
by definition, selection is evident in the two components of the
PA cycle, perception and action. Attention could rightfully be
considered the mother ofall cognitive functions. It selects certain
percepts, memories, motives, and actions at the expense of all
others, which are suppressed and inhibited (Fuster, 2003). But
again, this happens with or without consciousness, though con
sciousness is a constant phenomenon in the most demanding selec
tions. It happens as a result of the internal dynamics ofthe cortex,
without the need for a central executive. Certainly, the prefrontal
cortex serves attention, but merely as the mediator of selective
perception or action. Any control from this cortex over attention and over other cortical regions - derives exclusively from its
dynamic involvement in the PA cycle (Chapter 4).
In the human brain, selection - especially selective atten
tion - reaches into the future. The cerebral cortex selects percep
tual and executive cognits for goal-directed prospective action,
while other less relevant cognits are inhibited. Here evolution
Conversely, in sensoiy discrimination and in discriminating action, one
input, depending on certain features of it. can lead to different outputs.
"Desynchronization" is a characteristic of the cortical electroencephalogram
(EEG) in the awake state. It probably reflects the re-entrant activation of
multiple cognits. each at its own frequency range or "spectral fingerprint"
(SiegeletflL 2012).
45
46
Evolutionary roots of freedom
has endowed the human brain with the ultimate cortical appara
tus to do that prospective selection, in the full sense of the word
"ultimate": the prefrontal cortex. It is with the prefrontal cortex
that the human brain acquires its freedom to set goals and
purposes.
In science, teleology is a dirty word. It is also a logical incon
gruity, because it implies the temporal inversion ofcausality, which
is just about the worst possible anomaly in scientific discourse. Yet it
is extremely compelling to attribute to the prefrontal cortex a
teleological function. Things appear to happen in that cortex because
of a future event, whether that event is a course of future action, a
goal, a reward, or the answer to a request from somebody. Is a future
event the cause ofpresent action? Here the laws of physical causality
would seem to be turned backwards and upside down.
That is just an appearance, however. With the advent of the
prefrontal cortex, goals and purposes have entered the agenda of
the brain. On close examination, the teleological paradox dis
solves before our eyes, because the cause of future action is firmly
anchored in the past. That past, in the brain, consists of evolu
tionary and individual memory in the form of established drives
and imagined cognits of the future; it is the "memory of the
future" (Chapter 5). A better word for that land of teleology is
teleonomy (Monod, 1971), which, in essence, is a critical dimension
of liberty, perhaps in effect its most decisive dimension.
Teleonomy has been identified with life, as its future preservation
is the first objective of life itself.
Out of the "night of evolutionary time," Homo sapiens
emerged, the end result of countless interactions of countless
organisms with their environment. At the crux of those
interactions was a long and silent cycle of mutual influences
between genes and "environmental demand." By a process
that we do not understand, and probably never will, the brain of
Homo sapiens ("knowing man") acquired the means to foresee
and foretell the "demands" of the Umwelt (the world around)
and to change them in order to better adapt to it during his
life and that of his descendants. The PA cycle grew in complexity.
Surely there is a rudiment of it in other primates, but no more
than a rudiment (next section). With the human brain, the
Neural Darwinism
temporal period of the cycle increased by several orders of mag
nitude. So did the complexity of the agent, now the brain
itself, and the complexity of the environmental information it
was able to handle, and to predict. The prefrontal cortex devel
oped as the supreme neural predictor at the top of the cycle.
Language is an immense elaboration of animal communica
tion. It also emerged from the expansion of the prefrontal cortex
with its temporal organizing properties. Language became a marvelously suited means of closing the PA cycle between the brain
and the environment in the service of the self and others. With
language, the human brain became capable of formulating prob
abilities of future causality, to bias favorably those probabilities
with logic (Greek, logos, word) for the benefit of the self and
others, and to record changes, both past and projected into the
future. Language adds another decisive dimension to freedom
(Chapter 6).
The psychologist Gibson (1977) coined an interesting term,
ajfordance, which fits perfectly in the human PA cycle, especially
in its future perspective. Affordance is a quality of an object or
environment that allows a subject to perform an action. Thus,
affordances are action possibilities that the world offers to the
individual. I think the term and its definition are useful here, but
that definition should be expanded, as the human being is capa
ble of creating affordances and of projecting them on the environ
ment. New affordances can thus emerge from perception of the
environment in the light of prior experience - that is, in the light
of established cognits. The invented new cognits, projected on
that environment, can thus be incorporated in the PA cycle and
guide the action to the adaptive manipulation of its objects.
Affordances, therefore, are another means by which the prefron
tal cortex can imagine ("memorize") future action. Affordance is
yet another decisive dimension of freedom. The human being is
unique in that it can freely create his or her own affordances. As
we will see in the corresponding chapter (Chapter 6), language is
an extraordinarily fertile creator and vehicle of affordances. The
prefrontal cortex, the most advanced product of evolution in the
human brain, is the supreme enabler of both language and
affordances.
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Evolutionary roots of freedom
THE TWO TEMPORAL FACES OF LIBERTY
Just as Janus the Roman god had two faces, one looking
backwards and the other forwards, liberty has two temporal
perspectives, one lookingto the past and the other to the future.
The analogy hasbeenaptly applied to the conscious experience of
time, which has been called "mental time traveling," between the
past and the future. Now, applying it to liberty requires some
explanation.
Of course, we are not free to change the past, for the past is
"done." But the Janus analogy is valid with regard to freedom
because of the simple fact that, while we are not free to change
that past,we are free to choose parts of that past to make informed
choices for the future. Further, a chosen action is not only based
on prior experience, but it also engenders new experience to
inform future choice, thus completing the PA cycle.
In effect, however, the lion's share of prior experience at the
base of our freedom to make choices is not exclusively our own,
but belongsto the entire human species;it is made of our sensoiy
and motor systems. That common "experience" is built in the
genome and finds its expression in the physical anatomy of
those systems. For that reason, I call the structure of those sys
tems "phyletic memory." It is genetic memory in the form of the
nervous structures and mechanisms that are essential for ecolog
ical adaptation. Phyletic memory includes the peripheral recep
tors of primary sensations and the generators of elementary
movements for nourishment and defense.12
It should be apparent therefore that the term phyletic memory
is more than a figureofspeech, in that the memory it carries in its
very structure is the collective experience of the species in deal
ingwith the physical environment. It can be legitimately called
memory because it consists of "stored" information that, after
12 Tocallthe sensoryand motor systems"structural memory" makessense only
in evolutionary and ontogenetic terms. Surely it is fundamentally genetic
memory in the sense that the structure of those systems is encoded in our
genes.Even before birth, however, it is subject to environmental influences
upon the phenotype of those two systems.
The two temporal faces of liberty
critical neonatal periods of "rehearsal,"13 is retrieved and utilized
with every act of perception or overt action. The primary sensoiy
and motor cortices are part of that memory and comprise the
indispensable interface between evolutionary and individual
memory.14 It is through the functioning of phyletic memory in
those cortices that individual memory, perceptual and executive,
is formed and deposited in the cognitive networks (cognits) of
the cortex of association. Liberty rests on the potential selectivity
of those individual associative cortices, and it is logically
constrained by sensoiy or motor handicaps that affect their
phyletic base.
In any event, it is the cortex as a whole that makes the
choices that are the essence of individual liberty, not an extracortical or extracorporeal entity that we can identify as a choos
ing, deliberating, and willing I. The I is nothing other than the
cortex, selecting between inputs, some from the past and others
from the present, in order to select outputs of adaptive action.15
Thus, individual selection is no longer the natural selection that
served the population in evolutionary time; however, the cogni
tive choices of the individual crucially depend on that phyletic
history.
The selective cognitive networks of the cerebral cortex are
constantly under the influence from another store of phyletic
memory situated deep in the interior of the cerebrum: the
13 Duringcertain criticalperiodsshortly after birth, the senseand motor organs
have to be utilized to become fully functional from then on. Animals that
through those periods have been deprived of visual or auditory stimulation
become permanently impaired, visually or auditorily, because of faulty cort
ical development (Hensch, 2004).
M The primary motor and sensoiy cortices, while being the lowest and most
basic levels of phyletic cortical memory, are not the lowest stages of inherited
evolutionary sensors and effectors in the central nervous system. Arguably,
we have to descend to the spinal cord and to the nuclei of the autonomic
nervous system in the brainstem to find them. For it is in these structures
where lie the centers of reflex activity that regulate the most primitive,
innate, defensive, and nurturing mechanisms with which we adapt our
organism to the internal and external milieus.
15 Each cortical choice is the result of a massive process of computation of
inputs from many sources upon the association cortices, and ultimately the
prefrontal cortex. An important point here is that the prefrontal cortex
enables and mediates the action within the PA cycle, but is not the sole
generator of that action.
50
Evolutionary roots of freedom
emotional or limbic system or brain. The limbic system consists
of an array of interconnected neural masses and nuclei of ances
tral phylogenetic origin that critically intervenes in the imple
mentation of instinctual drives and emotional responses of the
organism to the environment, internal and external. The fore
most components of the limbic system are the hypothalamus, the
amygdala, and the hippocampus. The first two are implicated in
all instinctual behavior (feeding, sex, flight, defense, and aggres
sion), as well as in the acquisition, maintenance, and retrieval of
emotional memory - that is, the memory of likes and dislikes,
love and hate, reward and punishment, pleasure and pain
(Denton et al, 1996; Hess, 1954; Pessoa and Adolphs, 2010). The
hypothalamus and the amygdala are also directly or indirectly
connected with the autonomic nervous system and hormonal
systems, which play important roles in visceral control and emo
tion (Buijs and van Eden, 2000).
The hippocampus is a transitional ancestral structure situ
ated between the limbic brain and the neocortex. It is anatomi
callya portion of ancient cortex, folded onto itself and tucked in
the middle of the cerebral hemisphere on each side. In lower
mammals, it performs vital functions in olfaction, touch, and
spatial navigation.16 In primates, especially the human, the hip
pocampus plays a critical role in the acquisition, consolidation,
and retrieval of memoly of any modality (Squire, 1992).
Adjacent to the limbic brain are the basal ganglia (Aliens
Kappers et al, 1960), a conglomerate of neural structures, also
of early phylogenetic and ontogenetic development, that
critically intervene in voluntary, reflex, and automatic motility.
Connective loops that link the motor cortex, the cerebellum,
the thalamus, and the basal ganglia mediate the timely execution
16 Ithas always beensomewhatofa mysterywhythe hippocampusof rodents is
so critical for these three functions, whereas the human hippocampus is only
marginally involved in them. The reason, in my opinion, is because the
hippocampus of the rodent (which is the most advanced cortex the rodent
has) is in charge of the three functions inasmuch as they are essential to the
animal's survival, whereas in the human, those functions have migrated to
higher cortex for more flexibility and range of adaptation to a more complex
environment.
The two temporal faces of liberty
of voluntary - as well as automatic and well-rehearsed - motor
sequences (Alexander et al, 1992; Kreitzer and Malenka, 2008).
In conclusion, those internal parts of the brain, together
with primary sensoiy and motor cortices, in the aggregate, con
stitute the cerebral ground layer of phyletic memory. That struc
tural memory, including predispositions to action in the basal
ganglia, is the primordial neural apparatus for adaptation to the
environment. That environment includes the internal milieu,
which was selected in evolution to fulfill the most immediate
exigencies of survival and procreation of the species.
Freedom will rest on that fund of evolutionary experience,
while remaining also constrained by it. For, no organism, includ
ing the human, can surpass the limits imposed by the sensoiy
and motor capabilities it inherits. In other words, that heritage after critical postnatal periods - limits our senses to light, sound,
touch, olfaction, and taste within certain ranges of frequency,
intensity, and chemical composition. It also limits the range of
angle, direction, and bearing of each of our joints and limbs.
Thus, considering the genetic endowment ofour motor systems,
there are physical limits to the actions we can execute with
those systems. This remains true even after full development
and physical education.
Freedom will not only rest on, but also emerge from, that
primordial structural memory of sensoiy and motor systems,
visceral control systems, and emotional systems. The most imme
diate conditions permitting its emergence are the variance and
plasticity of those systems, and, most critically, the cognitive
networks of the cortex of association. In the individual human,
those systems and networks will provide the essential inputs to
the PA cycle, which moves us from one choice to the next, from
one decision to the next, and from one objective to the next. The
aggregate ofthose inputs constitutes the experience, phyletic and
personal, on which liberty is based. It is the major share of the
retrospective aspect of liberty.
How free are our choices of retrospective memory? They
are, and must by necessity be, only relativelyfree because they are
not free of physical and psychological constraints. Regardless
of those constraints, our freedom depends on, and is directly
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Evolutionary roots of freedom
related to, the availability of alternatives, whether we are
aware of them or not. We experience freedom even though and in part because - we are unaware of the degree to which
those alternatives steer our actions. This is not a blanket endorse
ment of determinism. On the contrary, having decoupled
cortical choice from consciousness, freedom asserts its independ
ence. Determinism is tempered in the variability and randomness
of a complex adaptive system such as the human cerebral cor
tex.17 But here the concept of "cortical choice" needs to be
qualified.
Choice implies alternative. But the alternatives of informa
tion that reach the cortex to literally inform action do so with
different degrees of intensity (synaptic strength) depending on a
variety of internal and external states or circumstances. Some
alternative inputs will be in conflict with one another; others
will potentiate each other. The inputs that prevail in the decision
to act will be the probabilistic result of competition or summa
tion of synaptic "weights," which will sway the cortex to one
action or another. Probability here is to be understood in the
Bayesian sense, in this manner applicable to the state of the
evidence or knowledge contained in any given set of inputs.1S
Ultimately, the weight of each input on a decision will be "deter
mined" according to an estimate of probability based on prior
knowledge and bearing on the synaptic weight of that input.19
As we have seen, alternatives of input will arrive in the
prefrontal cortex from many sources, some cortical and others
subcortical. Alternative sources of input will multiply if the
The concept of open adaptive system was first proposed by von Bertalanffy
(1950). the father of "general system theory" (GST), to account for the dynam
ics of organisms - biological and sociological - that tend to equilibrium or
steady state in the face of perturbations.They do it by use of self-correcting
feedback, among other mechanisms. Clearly, that cyberneticconceptapplies
to all self-regulationin the nervous system, and of course the PA cycle.
Bayesian probability, as distinguished from "frequential" probability, is the
logicbased on uncertain statements about a hypothesis and liable to change
by the acquisition of further data (jaynes et al., 2003).
The expression "synaptic weight" is meant here to encompass not only the
strength of present or potential electrochemical transactions at the mem
branes of nerve cells, but also the numbers of axon connections and other
input fibers arriving at those cell membranes.
The two temporal faces of liberty
actions informed by those inputs are complex and high in the
hierarchy ofthe PAcycle. Bycontrast, inputs of subcortical origin,
at the foundations of phyletic memory, will be simple and
straightforward, such as the urge to eat, fight, or mate. They will
arrive to the cortex by fiber paths funneled through the orbital
prefrontal cortex, which collects information about rewards with
biological "valence." Rarely, except in a sociopath, will those
impulses come to the cortex unaccompanied by inputs from
cortical networks representing social, ethical, and esthetic prin
ciples. Hence the formalities of dining, sport competition, and
courting.
Those natural impulses will come to our cortex also accom
panied by inputs from the cognitive networks that store our
episodic and semantic memory. Those too will be subject to
internal "competitive bidding" in the higher levels of the PA
cycle. Consider, for example, the many inputs that, in addition
to hunger, inform our choices of restaurant and menu: personal
experience, counsel from friends, cost, means of transportation,
parking availability, ethnic-food preference, and so on. All will
weigh on the choices.
In sum, on the retrospective side of liberty are the inputs to
the orbital prefrontal cortex from the internal milieu and its
limbic sources. Concomitantly, inputs from the cortex at large
converge on the cortical lateral convexity of the frontal lobe,
conveying to it information from the cognitive networks of
knowledge, personal memory, and social values. The prefrontal
cortex will reconcile and prioritize those inputs before each deci
sion. Completing the PA cycle, the prefrontal cortex will also
reconcile and prioritize the consequences of each action for fur
ther action. The reconciling and prioritizing will be done in and
by the cortex itself. Those operations will take place in a multi
variate and probabilistic environment of synaptic connections of
widely differing and variable weights. It is the relative internal
configuration of those weights with respect to one another that
will lead to one alternative of action or to another. The root of the
decision, therefore, is to be found in all its antecedents and the
relative synaptic weights of each of their respective neural
foundations.
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Evolutionary roots of freedom
EVOLUTION OPENS MAN AND WOMAN TO THEIR
FUTURE
Inseparable from the retrospective aspect of freedom is its
prospective aspect, which willbe further discussed in Chapter 5.
The two are two sides of the same coin, namely, of the dynamics
of the PA cycle, which by definition has a past and a future
alternating with each other. Both are anchored in phyletic
memory, from which the selectivity of individual human
cognition flows. Arguably, action precedes perception, in phylo
geny as well as ontogeny. Just as evolution selects from genetic
variance "actions" that are adaptive for the population, the
human infant enters the world palpating it to select certain
"adaptive" stimuli within it. It is by haptics - active touch - that
the newborn finds the mother's breast. Crying, which is another
phyletic action, will rapidly join haptics in the PA cycle of infant
nourishment.20
With the evolution ofthe cerebral cortex in general, and the
prefrontal cortex in particular, the PA cycle of the human begins
early in life to workat higherlevels of complexity for the benefit
of the individual and, eventually, society as well. Liberty will
emerge from the expansion of both the fund of alternatives of
information available to the cortex and the alternatives of action
to which that information can lead.
Among the alternatives of action, none is as relevant to
liberty as those that evolve in the fields of cognition most charac
teristic of the human being: planning and language. Here we have
to address a question that often arouses endless controversies.
Are there precursors of planning and language present in the
animal kingdom before man? The most immediate - and least
controversial - species to queiy in this respect are the great apes.
Away to assess the ability to plan behavioris to examine the
ability to use tools, since tool use invariably implies a certain
sequence of personal actions that is reasoned, goal-directed, and
20 Later, "babbling" and the rudiments of languagewill be incorporated in the
PA cycle betweenthe childand the environment presidedover bythe mother
(Chapter 6).
Evolution opens us to our future
not innate. For several years around the time ofWorld War I, Kohler
(1925), a noted gestalt psychologist, studied meticulously the reason
ing potential of chimpanzees in a colony of such animals he main
tained on one of the Canary Islands. One of his smartest subjects.
Sultan, learned to stack boxes on winch to stand and to use poles to
reach high-hanging bananas. From this Kohler concluded that the
animal was able to reason to some degree and to use intermediary
objects to attain spatially distant goals.
Whether Sultan planned actions or used tools in the strict
sense of these words has been extensively debated. It is unques
tionable, however, that the animal was capable of a degree of
prospective and purposive reasoning. It is also unquestionable
that he learned or had the intuition to use "tools" to attain his
goal. Lower primates are capable of doing both, though to a lesser
degree. Later studies, furthermore, have shown that the great
apes are capable of cognitive "time-traveling" and foresight, as
they can display sequential actions to reach goals that are distant
in space and time (Osvath and Osvath, 2008). The argument that all
those operations are the result of associative learning is idle,
because there is no foresight or tool use of any kind without
some degree of prior associative experience. In fact there is no
liberty to act reasonably one way or another without prior empir
ical knowledge of context and consequences.
Thus, there is rudimentary planning and foresight in the
earlier primates. However, because humans exceed those capa
bilities by many orders of magnitude, it has been mistakenly
argued that those capabilities are the exclusive patrimony of
our species. Similar arguments and counterarguments have
been made with respect to language, albeit usually with more
vehemence on both sides. The most obvious question in this
respect is whether the vocalizations of nonhuman animals qual
ify as evolutionary precursors of language. The answer is yes,
insofar as those vocalizations consist in means of communication
between conspecifics, like language. Another, more relevant,
question is whether animals possess some primitive form of
language. The answer here is definitely no, as animals, while
able to communicate with symbols, cannot communicate with
logical reasoning, which is an essential attribute of language.
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Evolutionary roots of freedom
With language and the enormous expansion of the cerebral
cortex that goes with it, comes the unique tool that more than any
other allows humans to fashion their future: speech. This is the
supreme maker of affordances, a la Gibson (1977). It is not a
coincidence of nature that that "ultimate tool" (Greenfield,
1991) develops together with a region of the frontal cortex that
is heavily involved in tool malting and utilization.21 Nor is it
coincidental that the entirety of the frontal cortex, where that
area is located, serves not only speech but also, more broadly,
what Lashley (1951) called the "syntax of action." Indeed, by
speech, evolution comes around to furthering an unwritten "pur
pose" of the evolution of the species: the freedom to ensure its
own survival. For it is by the written word that the human race
codifies the liberty of its progeny.
CONCLUSIONS
Our freedom and ability to shape our future are the ultimate
offspring ofthe extraordinary evolution of the human brain. Both
freedom and creativity have their most recent evolutionary root
in the prefrontal cortex, the latest domain of the cerebral mantle
to attain structural maturity, in evolution as in individual
development.
Critical for both human prerogatives, freedom and future, is
the rich connectivity that develops between prefrontal cell pop
ulations, as well as between them and those in other cortical
regions. Because of the inherent synaptic plasticity of that con
nectivity, cognitive networks (cognits) will be formed by life
experience in the associative cortex, which will codify the mem
ory of the individual and inform his decisions to reach his goals
(Chapter 3).
Freedom flourishes with the capacity of the cortex to choose
between memory networks and between action networks in the
pursuit of chosen goals. In all instances, the pursuit of a goal takes
21 The area in question includes Broca's area and a large portion of the premotor
cortex, both adjacent to each other in the frontal lobe of the left or dominant
cerebral hemisphere.
Conclusions
place within the dynamics of a PA cycle that runs through the
posterior cortex, the prefrontal cortex, and the environment, and
back to the cortex in a circular fashion until the goal is reached.
In parallel with that cognitive cycle and interacting with it, a
deeper and older cycle processes emotions and instinctual urges
through the limbic system. The orbital prefrontal cortex is an
integral part of that cycle, which feeds emotional and instinctual
influences into the cortex at large. Because reactions to those
influences are biologically rooted and weigh heavily on our deci
sions, the limbic system constitutes the most primordial evolu
tionary root of liberty in the human brain.
Liberty, in general, has two major components with oppo
site temporal perspective; the first is the ability to choose experi
ence from the past, and the second is the ability to choose the
future based on the chosen past. The two alternate in tandem
with each other under the prefrontal cortex, which integrates
past with future at the top of the PA cycle (Chapter 4). The most
essentially human is the second, the capacity of the prefrontal
cortex to predict events, as well as to select, decide upon, plan,
prepare for, and organize goal-directed actions in the immediate
or distant future (Chapter 5). Among those actions is spoken and
written language, the truly unique patrimony ofour species at the
service of all our freedoms and our creative power (Chapter 6).
57